Temperature feedback control for solid state gas sensors

Abstract

A solid state gas sensor may include gas sensing element coupled to a substrate. The gas sensing element may have a desired operating temperature, which may be between 100 and 400 degrees Celsius. The sensor may further include a temperature sensor coupled to the substrate and configured to sense an operating temperature of the sensing element and provide a feedback signal representative of the operating temperature. The sensor may further include a heater having a heat output. The heater may be responsive to the feedback signal to adjust the heat output to drive the operating temperature to the desired operating temperature. A detector such as a smoke detector or carbon monoxide detector having such a solid state gas sensor is also provided. An associated method is also provided.

1 . A solid state gas sensor comprising: 
 a gas sensing element having a desired operating temperature, said gas sensing element coupled to a substrate;    a temperature sensor coupled to said substrate and configured to sense an operating temperature of said gas sensing element and provide a feedback signal representative of said operating temperature; and    a heater having a heat output, said heater responsive to said feedback signal to adjust said heat output to drive said operating temperature toward said desired operating temperature.    
   
   
       2 . The solid state gas sensor of  claim 1 , wherein said heat output of said heater is adjusted by varying a heater current level of said heater.  
   
   
       3 . The solid state gas sensor of  claim 2 , further comprising a temperature feedback control circuit coupled to said temperature sensor and said heater, said temperature feedback control circuit comprising a comparator to compare a first signal representative of said feedback signal with a reference signal and provide an output signal representative of a difference between said feedback signal and reference signal, said heater configured to adjust said heat output of said heater in response to said output signal.  
   
   
       4 . The solid state gas sensor of  claim 3 , wherein said temperature feedback control circuit further comprises a transistor having a control electrode, said control electrode responsive to said output signal from said comparator to adjust a current level of said heater to adjust said heat output of said heater.  
   
   
       5 . The solid state gas sensor of  claim 1 , wherein said temperature sensor comprises a platinum temperature sensor and said heater comprises a platinum heater.  
   
   
       6 . The solid state gas sensor of  claim 1 , wherein said desired operating temperature is between 100 and 400 degrees Celsius.  
   
   
       7 . A detector comprising: 
 a solid state gas sensor configured to detect a concentration of a gas in air monitored by said detector, said solid state gas sensor comprising a gas sensing element having a desired operating temperature, said gas sensing element coupled to a substrate, said solid state gas sensor further comprising a temperature sensor coupled to said substrate and configured to sense an operating temperature of said gas sensing element and provide a feedback signal representative of said operating temperature, said solid state gas sensor further comprising a heater having a heat output, said heater responsive to said feedback signal to adjust said heat output to drive said operating temperature toward said desired operating temperature; and    an alarm configured to activate when a concentration of said gas in said air exceeds a threshold value.    
   
   
       8 . The detector of  claim 7 , wherein said heat output of said heater is adjusted by varying a heater current level of said heater.  
   
   
       9 . The detector of  claim 8 , wherein said solid state gas sensor further comprises a temperature feedback control circuit coupled to said temperature sensor and said heater, said temperature feedback control circuit comprising a comparator to compare a first signal representative of said feedback signal with a reference signal and provide an output signal representative of a difference between said feedback signal and reference signal, said heater configured to adjust said heat output of said heater in response to said output signal.  
   
   
       10 . The detector of  claim 9 , wherein said temperature feedback control circuit further comprises a transistor having a control electrode, said control electrode responsive to said output signal from said comparator to adjust a current level of said heater to adjust said heat output of said heater.  
   
   
       11 . The detector of  claim 7 , wherein said temperature sensor comprises a platinum temperature sensor and said heater comprises a platinum heater.  
   
   
       12 . The detector of  claim 7 , wherein said desired operating temperature is between 100 and 400 degrees Celsius.  
   
   
       13 . A method comprising: 
 monitoring an operating temperature of a gas sensing element of a solid state gas sensor, said gas sensing element having a desired operating temperature;    providing a feedback signal representative of said operating temperature; and    adjusting a heat output of a heater in response to said feedback signal to drive said operating temperature of said gas sensing element toward said desired operating temperature.    
   
   
       14 . The method of  claim 13 , further comprising adjusting said heat output of said heater by controlling a heat current level of said heater.  
   
   
       15 . The method of  claim 13 , wherein said temperature sensor comprises a platinum temperature sensor and said heater comprises a platinum heater.  
   
   
       16 . The method of  claim 13 , wherein said desired operating temperature is between 100 and 400 degrees Celsius.